The present invention relates to a system and method for registering in a remote communication terminal and a communication peer an encryption key, or secret key, which is used for cryptographic communication performed between the remote communication terminal and communication peer.
In the prior art, an electronic key system for a vehicle includes a portable key device, which transmits a unique key code through wireless communication. The vehicle key system is a wireless door lock system and/or key operation-free system. In a wireless door lock system, an in-vehicle device locks and unlocks the vehicle doors when a button on a remote portable key device is operated. In a key operation-free system, when receiving a request signal from a vehicle, a portable key device returns an ID code to the vehicle. When the returned ID code is authenticated, an in-vehicle device locks or unlocks the doors. The in-vehicle device may also permit starting of the engine or actually start the engine.
For the ID code transmitted from the portable key device to be secure against eavesdropping or tampering, the vehicle electronic key system performs cryptographic communication. Japanese Laid-Open Patent Publication No. 2004-300803 describes an electronic key system that uses a secret key code (shared key code) technique. In the secret key code technique, an encryption key held by a sender is the same, or shared, by a decryption key held by a recipient. This secret key technique, in which the sender and the recipient uses the same key, is advantageous in that the encryption and decryption processing speeds are high and is thereby widely used in cryptographic communication for vehicles.